Method for improved critical dimension uniformity in a semiconductor device fabrication process

ABSTRACT

Exemplary methods of patterning a device layer are described, including operations of patterning a protector layer and forming a first opening in a first patterning layer to expose a first portion of the protector layer and a first portion of the hard mask layer, which are then are exposed to a first etch to form a first opening in the first portion of the hard mask layer. A second opening is formed in a second patterning layer to expose a second portion of the protector layer and a second portion of the hard mask layer. The second portion of the protector layer and the second portion of the hard mask layer are exposed to an etch to form a second opening in the second portion of the hard mask layer. Exposed portions of the device layer are then etched through the first opening and the second opening.

PRIORITY DATA

The present application is a continuation application of U.S.application Ser. No. 16/042,240, filed Jul. 23, 2018, which is acontinuation application of U.S. application Ser. No. 15/169,249, filedMay 31, 2016, now U.S. Pat. No. 10,032,639, each of which is herebyincorporated by reference in its entirety.

BACKGROUND

The semiconductor integrated circuit industry has experienced rapidgrowth in the past several decades. Technological advances insemiconductor materials and design have produced increasingly smallerand more complex circuits. These material and design advances have beenmade possible as the technologies related to processing andmanufacturing have also undergone technical advances. In the course ofsemiconductor evolution, the number of interconnected devices per unitof area has increased as the size of the smallest component that can bereliably created has decreased.

A semiconductor wafer is processed by a semiconductor manufacturer toform various integrated circuits (IC) in different regions of the wafer.The wafer includes a substrate with many patterned material layersthereon that form the discrete devices that make up a circuit.Variations in pattern density over the different regions can causevarious issues including critical dimension (CD) variation or CDuniformity. As the node or scale of the semiconductor fabricationdecreases to advanced technologies, such as from 45 nm to 32 nm and to28 nm, the functionalities of an IC device are more sensitive to the CDvariations and uniformity. For example, dense lines and isolated linesare common in IC layout and cannot be avoided by the design rules.However, as the feature size decreases, high fidelity replication ofsuch mask features into an underlying material layer can be problematic.Additionally, as the technologies have advanced, some currently useapproaches may have limited effectiveness and applicability. Therefore,there is a need of methods to address such issues.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features, whether on the devices or the wafersand semiconductor features described herein, may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a flowchart of a method of patterning a device layer,according to aspects of the present disclosure.

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H are top view illustrations of aportion of a semiconductor wafer undergoing processing according to anembodiment of the method of FIG. 1, according to aspects of the presentdisclosure.

FIG. 3 is a flowchart of another method of patterning a device layer,according to aspects of the present disclosure.

FIGS. 4A, 4B, 4C, 4D, 4E, 4F, and 4G are top view illustrations of aportion of a semiconductor wafer undergoing processing according to anembodiment of the method of FIG. 3, according to aspects of the presentdisclosure.

FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, and 5I are top view illustrationsof a portion of a semiconductor wafer undergoing processing according toanother embodiment of the method of FIG. 3, according to aspects of thepresent disclosure.

FIG. 6 is a flowchart of another method of patterning a device layer,according to aspects of the present disclosure.

FIGS. 7A, 7B, 7C, 7D, 7E, 7F, 7G, and 7H are top view illustrations of aportion of a semiconductor wafer undergoing processing according to anembodiment of the method of FIG. 6, according to aspects of the presentdisclosure.

FIGS. 8A, 8B, 8C, 8D, 8E, 8F, 8G, and 8H are top view illustrations of aportion of a semiconductor wafer undergoing processing according toanother embodiment of the method of FIG. 6, according to aspects of thepresent disclosure.

These figures will be better understood by reference to the followingdetailed description.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

It is understood that several processing operations and/or features of adevice may be only briefly described, some such operations and/orfeatures being known to those of ordinary skill in the art. Also,additional processing steps or features can be added and certain of thefollowing processing steps or features can be removed and/or changedwhile still implementing the claims. Thus, the following descriptionshould be understood to represent examples only, and are not intended tosuggest that one or more steps or features is required in everyembodiment.

Referring now to FIG. 1, illustrated therein is a flowchart of a method100 of patterning a device layer during a semiconductor devicefabrication process. As illustrated, the method 100 includes severalenumerated steps or operations. Embodiments of the method 100 mayinclude additional steps or operations before, after, in between, or aspart of the enumerated steps or operations shown in FIG. 1. Someembodiments of the method 100 may omit one or more of the enumeratedoperations. The method 100 may be performed in a semiconductor devicefab, which may include many different fabrication tools including dryand immersion photolithography tools, etching chambers or etchant tanksto perform dry and or wet etching processes, cleaning tools, depositiontools, etc.

An embodiment of the method 100, as illustrated in FIG. 1, may begin atoperation 102 in which a protector layer, disposed over a hard masklayer, is patterned. The protector layer may be patterned by aphotolithographic process in which a photoreactive material layer isformed over the protector layer. The photoreactive material layer isexposed to radiation energy, such as extreme ultraviolet light, and thendeveloped to reveal a pattern corresponding to the exposure. An etchingprocess may remove exposed portions of the protector layer defined bythe pattern in the photoreactive material layer.

At operation 104, a first opening in a first patterning layer may beformed to expose a first portion of the protector layer and the firstportion of the hard mask layer underneath the protector layer. Atoperation 106, the first portion of the protector layer and the firstportion of the hard mask layer may be exposed to a first selective etchprocess to form a first hard mask layer opening in the first portion ofthe hard mask layer. The etch process may be selective in that etchingof the hard mask layer occurs at a significantly higher rate, such as anorder of magnitude higher, than any etching of the protector layer whichmay occur.

At operation 108, a second opening may be formed in a second patterninglayer to expose a second portion of the protector layer and the secondportion of the hard mask layer. This operation may be performed by aphotolithographic process as described with respect to operation 104. Atoperation 110, the second portion of the protector layer and the secondportion of the hard mask layer may be exposed to a second selective etchto form a second hard mask layer opening in the second portion of thehard mask layer. After the formation of the first and second hard masklayer openings, an etch process may be performed to exposed portions ofthe device layer through the first and second hard mask layer openings,at operation 112.

For clarity of explanation, the method 100 is further described hereinwith respect to the top view illustrations of a semiconductor wafer 201in FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, and 2H. FIG. 2A is a top view of aportion of a substrate 200 of the wafer 201. The wafers and substratesdescribed herein may take various forms including but not limited towafers (or portions thereof) or substrates of individual devices such aschips (e.g., fabricated on a wafer). Various features may be formed onthe substrate 200 by the addition, subtraction, and alteration ofmaterial layers formed on the substrate to produce integrated circuitsincluding those formed by CMOS-based processes, MEMS devices, imagesensors, and the like. While the wafer 201 and substrate 200 may becircular when viewed from above in its entirety, only a portion of thewafer 201 and substrate 200 is shown in FIG. 2A. In some embodiments,the substrate 200 may include one or more layers thereon such that theillustrated layer labeled “200” in FIG. 2A is a material layer disposedover the substrate of wafer 201.

Referring now to FIG. 2B, shown therein is a patterned device layer 202.As illustrated, the patterned device layer 202 includes a series ofparallel lines including parallel lines 202A, 202B, 202C, 202D andothers which are collectively referred to as the device layer 202. Insome embodiments, the parallel lines of the patterned device layer maybe separate from each other by less than 10 nm. For example, thesubstrate 200 may be a silicon oxide layer and the patterned devicelayer may include parallel lines formed from polysilicon. The substrate200 and the device layer 202 may be formed from other materials in otherembodiments of the present disclosure. In some embodiments, the devicelayer may be a masking layer that needs to be patterned further byanother patterning process due to process constraints or may havefeatures sufficiently small (for example, features 16 nm or less) thatadequate critical dimension uniformity is difficult to obtain. Forexample, the lines 202A-D of the device layer 202 may need to be cut.

Referring now to FIG. 2C, shown therein is an intermediate, sacrificiallayer referred to as hard mask layer 204. The hard mask layer 204 may bea silicon nitride layer, a silicon oxide layer, a metal layer, a metaloxide layer, a metal nitride layer or other material layer that coversthe exposed portions of the substrate 200 and the device layer 202 shownin FIG. 2B. The lines 202A-D and other patterned lines of the devicelayer 202 are illustrated with the dashed lines shown in FIG. 2C to showtheir approximate location on the wafer 201.

Referring now to FIG. 2D, shown therein is a patterned protector layer206, as may be formed in operation 102. The protector layer 206 may beformed from silicon nitride, in some embodiments, and formed from othermaterials in other embodiments. As shown, the protector layer 206 ispatterned with a “checkerboard” pattern such that repeating arrays ofopenings in the protector layer 206 are arranged in offset rows,resembling a checkerboard or chessboard. As illustrated, the openings inthe protector layer 206 are generally rectangular in shape having aminor axis and a major axis, while the remaining portions of theprotector layer 206 are substantially square, i.e. having two equalaxes. Other embodiments of the protector layer 206 may have differentgeometries for the openings such that the remaining portions havedifferent geometries as well. The openings in the protector layer 206may expose the hard mask layer 204 which may be positioned directlyunder the protector layer 206 such that the protector layer 206 directlycontacts the hard mask layer 204.

Referring now to FIG. 2E, shown therein is a first patterning layer 208with a plurality of windows or openings 210A, 210B, and 210C,collectively referred to as openings 210. At operation 104 of the method100, the first patterning layer 208 may be formed as a layer ofphotoreactive material, such as photoresist. The photoresist may be apositive or negative photoresist. The photoresist may be selectivelyexposed to radiation, such as by an ArF laser source or other radiationsource, including extreme ultraviolet radiation sources, such that onlythe portions defined by photomask features corresponding to openings210A, 210B, and 210C are exposed (if a positive photoresist) or arecovered (if a negative photoresist). In some embodiments, the firstpatterning layer 208 may be another material layer, such as siliconoxide, silicon nitride, or another patterning layer that is firstpatterned using a layer of photoresist and then is used to patternunderlying layers, like hard mask layer 204.

The openings 210 and the protector layer 206 combine to define windowsor openings, like the exemplary opening 212. As illustrated in FIG. 2E,multiple openings like the exemplary opening 212 are formed by theoverlapping geometries of the protector layer 206 and the openings 210.When a selective etch is performed, at operation 106, that etchesexposed portions of the hard mask layer 204 without significantlyetching the portions of the protector layer 206 exposed by the openings210, or the device layer 202 beneath the hard mask layer 204. Forexample, the etch process may remove the hard mask layer 204 at an etchrate that is an order of magnitude, or more, faster than the etch rateof the protector layer 206. The etch process may be a wet etch or dryetch. The formation of the exemplary opening 212 may be a firstpatterning to the hard mask layer 206.

Referring now to FIG. 2F, shown therein is a second patterning layer214. The second patterning layer 214 may be a photoreactive layerformed, at operation 108, over the substrate 200, the device layer 202,the hard mask layer 204, the protector layer 206, and any otherintervening layer. Before the second patterning layer 214 is formed, thefirst patterning layer 208 may be removed by a stripping process oretching process. The second patterning layer 214 may be patterned toform windows or openings 216, including individual openings 216A, 216B,216C, and 216D. The overlapping geometries of the openings 216 and theprotector layer 206 combine to form areas that define windows oropenings, like the exemplary opening 218. Exposing the wafer to anotherselective etch process may remove exposed portions of the hard masklayer 204, at operation 110. The exemplary opening 218 and other similaropenings as described are transferred into the hard mask layer 204 bythe selective etch process. As shown, the selective etch process hasbeen performed such that the opening 218 shows parallel lines 202C and202D of the device layer 202 and a portion of the substrate 200.

FIG. 2G illustrates the wafer 201 after removal of the second patterninglayer 214 and the protector layer 206. Accordingly, the hard mask layer204 is shown along with the opening 218 and the opening 212, and otherassociate openings, formed therein to expose portions of the devicelayer 202, including the parallel lines 202A-D and the others shown inFIG. 2G. Portions of the parallel lines 202A-D that are covered by thehard mask layer 204 are shown by the dashed lines. Exposed portions ofthe parallel lines 202A-D can be seen in the openings 212, 218, andothers. An etch process may be performed to etch portions of the devicelayer 202, such as the exposed portions of the parallel lines 202A-D,through the openings 212 and 218 and the other illustrated openings inthe hard mask layer 204, as described in operation 112 of FIG. 1. Thisetch process may “cut” the parallel lines 202A-D and other parallellines of the device layer 202 as shown in FIG. 2H. Afterwards, the hardmask layer 204 may be removed by a different etch process, also as shownin FIG. 2H. FIG. 2H further includes dashed line representations of theopenings 212, 218, and others used to cut the parallel lines 202A-D ofthe device layer 202.

Referring now to FIG. 3, shown therein is a flowchart of a method 300 ofpatterning a device layer in a semiconductor device fabrication processthat provides improved critical dimension uniformity. Like method 100 ofFIG. 1, the illustrated embodiment of method 300 includes severalenumerated steps or operations. Embodiments of the method 300 mayinclude other operations before, after, in between, or as part of theenumerated operations. Additionally, some embodiments of the method 300may omit one or more of the enumerated operations.

Accordingly, an embodiment of the method 300 may begin at operation 302when a first protector layer disposed over a hard mask layer ispatterned, such as by a photolithography process and a subsequent etchprocess. At operation 304, a first opening in a first patterning layermay be formed in order to expose a portion of the first protector layerand a first portion of the hard mask layer. At operation 306, aselective etch process may be performed to etch the portion of the firstprotector layer and the first portion of the hard mask layer etch toform a first hard mask layer opening in the hard mask layer. Because theetch process of operation 306 is a selective etch process, the exposureto the etch process may have a greater effect on the first portion ofthe hard mask layer then on the first protector layer, such thatrelatively little thickness of the first protector layer is removed bythe etch process, while the entire thickness of the first portion of thehard mask layer is removed.

At operation 308, a second protector layer disposed over the hard masklayer may be patterned by photolithography and etching or by anothersuitable process. In some embodiments, the second protector layer isformed from the same material from which the first protector layer isformed. A second opening and a second patterning layer may be formed toexpose a portion of the second protector layer and a second portion ofthe hard mask layer, at operation 310. At operation 312, the portion ofthe second protector layer and the second portion of the hard mask layermay be exposed to a second selective etch in order to form a second hardmask layer opening in the hard mask layer. At operation 314, an etchprocess may be performed to etch the exposed portions of the devicelayer through the first hard mask layer opening and the second hard masklayer opening.

To more clearly describe some embodiments of the method 300, referenceis made herein to FIGS. 4A-H, which are top view illustrations of aportion of a wafer 401 during a fabrication process like that of themethod 300. As shown in FIG. 4A, the illustrated portion of the wafer401 is similar in some respects to the wafer 201 as shown in FIG. 2C.Accordingly, the wafer 401 has a substrate 400 (or another top surfaceof the material layer formed over the substrate) with a device layer 402there on may be a patterned material layer. The device layer 402 may bea masking layer to be used to pattern a layer between the device layer402 and the substrate 400 in some embodiments. As shown in FIG. 4A, thepatterned device layer 402 is represented by a plurality of dashed-linefeatures, which are positioned beneath the device layer 402. A patternedprotector layer 406 is shown as including protector layer features 406A,406B, and 406C. As illustrated, the patterned protector layer 406includes generally rectangular, elongate features that extend parallelto the parallel lines of the device layer 402. Other embodiments mayinclude protector layer features of different shapes, which may be notbe oriented parallel to the parallel lines of the device layer 402.Similarly, the device layer 402 may be patterned with other patterns,instead of the pattern of parallel lines depicted in FIG. 4A (and inFIG. 2C). The protector layer 406 may be formed from silicon oxide,silicon nitride, or another material that may serve as an etch stop oretch mask during semiconductor fabrication. In the illustratedembodiment, the protector layer 406 and the hard mask layer 404 areformed from different materials. In some embodiments, the protectorlayer 406 and the hard mask layer 404 may be formed from the samematerial, and the additional thickness of the added protector layer 406may be utilized to prevent etching beneath the area defined by theprotector layer 406 when the hard mask layer 404 is attached.

Referring now to FIG. 4B, shown therein is the wafer 401 as illustratedin FIG. 4A and further including a first patterning layer 408. The firstpatterning layer 408 may be a photoresist layer or other photoreactivelayer that can be patterned by photolithographic processes. Asillustrated in FIG. 4B, the patterning layer 408 may be patterned, atoperation 304, to form openings 410A, 410B, and 410C, collectivelyreferred to as openings 410. As shown in FIG. 4B, the openings 410expose portions of protector layer features 406A, 406B, and 406C, aswell as portions of the underlying hard mask layer 404. The geometriesof the openings 410 combine with the geometries of the protector layer406 to produce openings like the exemplary opening 412 that expose thehard mask layer 404. A total of six openings like the exemplary opening412 are shown in FIG. 4B. Other embodiments may include more or feweropenings. Additionally, while the shape of the opening 412 isrectangular, other shapes and other patterns of shapes may be present inother embodiments.

Referring now to FIG. 4C, shown therein is a result of an etch processlike that of operation 306 of method 300, which forms the opening 412through the hard mask layer 404. Six total openings, like the opening412, are shown as being formed through the hard mask layer 404, therebyexposing the underlying substrate 400 and some of the parallel lines ofdevice layer 402. The etch process that forms the opening 412 shown inFIG. 4C, may be a first selective etch process that uses both the firstpatterning layer 408 and the first protector layer 406 to provide anetch mask. While the etchant more rapidly etches through the hard masklayer 404, the etchant etches comparatively slowly through the firstpatterning layer 408 and the first protector layer 406, if it etches thefirst patterning layer 408 and the first protector layer 406 at all.

After the formation of the opening 412 and other openings correspondingto the first patterning layer 408 and the first protector layer 406, asecond protector layer 414 may be formed over the surface of the wafer401, as part of operation 308. The protector layer 414 may cover theopenings formed in the hard mask layer 404 during operation 306. Theprotector layer 414 may include protector layer features 414A and 414Bthat correspond in geometry to the protector layer features 406A-C, suchthat the protector layers 406 and 414 are complementary to each other,forming a complementary pattern. For example, the distance between theprotector layer features 406A and 406C may be approximately the same asthe short dimension of protector layer feature 414B. In someembodiments, the short dimension of the protector layer feature 414B maybe greater than the distance between the protector layer features 406Aand 406C by less than 100 nm, less than 50 nm, less than 20 nm, etc.

Referring now to FIG. 4E, shown therein is a result of operation 310 ofmethod 300. A second patterning layer 416 is formed over the wafer 401.For example, the second patterning layer 416 may be a photoresist layeror other sacrificial layer that is formed over the exposed portions ofthe hard mask layer 404 and the second protector layer 414. Asillustrated, the second patterning layer 416 includes openings 418A,418B, 418C, and 418D, collectively referred to as openings 418. Theopenings 418 are elongate features in the depicted embodiment. Otherembodiments may include other geometries for the openings 418. Theoverlapping geometries of the openings 418 and the underlying secondprotector layer 414 forms a plurality of openings, including theexemplary opening 420. The hard mask layer 404 may be seen through theplurality of openings defined by the combination of the patterned secondpatterning layer 416 and the second protector layer 414.

At operation 312, the wafer 401 as shown in FIG. 4E may be subjected toan etch process. The etch process may be a second selective etch towhich the portion of the second protector layer and the second portionof the hard mask layer are exposed. The etch process may etch awayexposed portions of the hard mask layer 404 shown in the exemplaryopening 420 and other similar windows formed in the hard mask layer 404.The opening 420 may be the second hard mask layer opening describedabove in connection with operation 312 of method 300. As can be seenillustrated in FIG. 4F, a total 18 openings, like the opening 420 may beformed in the hard mask layer 404 such that portions of the substrate400 and the device layer 402 are exposed.

The hard mask layer 404 may act as an etch mask during a subsequent etchprocess to cut the parallel lines (or other features in otherembodiments) of the device layer 402, at operation 314. A result of thiscutting of the device layer 202 may be seen in FIG. 4G, which shows aportion of the wafer 401. As can be seen from FIGS. 4F and 4G, theopenings in the hard mask layer 404 may be used to cut pairs of parallellines of the device layer 402. In some embodiments, the openings in thehard mask layer 404 may be differently sized, such that some openingscause only a single parallel line or feature of the device layer 402 tobe cut or three or more features of the device layer 402 may be cut. Thecritical dimension uniformity may be improved over known methods byimplementing embodiments of the method 300.

Referring now to FIGS. 5A-I, shown therein are a plurality of top viewillustrations of a portion of a wafer 501 during a patterning process ofa device layer, like the method 300 of FIG. 3. FIGS. 5A-H provideanother embodiment that further describes the method 300 of FIG. 3. Asshown in FIG. 5A, the wafer 501 may include a hard mask layer 504disposed over a patterned device layer 502, represented by the dashedlines, with a substrate 500 or other material layer underlying thedevice layer 502, including a material layer to be patterned using thedevice layer 502 as a masking layer. The wafer 501 may be similar inmany respects to the wafer 201 as illustrated in FIG. 2C.

At operation 302, a first protector layer 506 may be formed over thehard mask layer 504 and patterned using photolithographic techniques, asshown in FIG. 5B. The pattern of the first protector layer 506 mayinclude protector layer features 506A, 506B, 506C, and others. Asillustrated, the protector layer features 506A-C may be elongate inshape and may be oriented in parallel with the parallel lines of thedevice layer 502. The protector layer 506 may be formed of a differentmaterial than the hard mask layer 504, such that the protector layer 506and the hard mask layer 504 have different etch rates for some etchantsand/or etch processes.

Referring now to FIG. 5C, shown therein is a first patterning layer 508formed over the protector layer 506 and the hard mask layer 504. Thefirst patterning layer 508 may be a photoreactive layer that hasundergone a photolithographic process to generate openings 510A, 510B,and 510C, collectively referred to as openings 510. The openings 510 ofFIG. 5C are elongate features that extend orthogonally to the parallellines of the device layer 502, and may be formed at operation 304 in anembodiment of method 300. The openings 510 exposed portions of the hardmask layer 504 and the protector layer 506. The overlapping geometriesof the protector layer 506 and the first patterning layer 508 form aplurality of windows or openings, like the exemplary opening 512. Asillustrated in FIG. 5C, the protector layer 506 and the first patterninglayer 508 combined to form six openings that leave portions of the hardmask layer 504 exposed. At operation 306, the wafer 501 may be exposedto an etch process. While portions of the hard mask layer 504 (definedby the opening 512 and other such openings) and the protector layer 506may be exposed to the etch process, the selectivity of the etch processmay result in substantially more etching of the hard mask layer 504 thanof the protector layer 506.

A result of the operation 306 may be shown in FIG. 5D, which shows thesubstrate 500 and portions of the device layer 502 in the opening 512and other comparable openings. The first patterning layer 508 may beremoved from the wafer 501 in preparation for further processing. Asshown in FIG. 5E a spacer material may be deposited over the surface ofthe wafer 501, to form spacer features 514A, 514B, 514C, and 514D,collectively spacer features 514. One spacer may be formed on each sideof the protector layer features 506A-C, such that the spacer features514 are partially defined by the protector layer 506. The spacerfeatures 514 cover portions of the exposed hard mask layer 504 as wellas portions of the device layer 502 and the substrate 500. As can beseen in FIG. 5E, a portion of the substrate 500 may remain uncovered bythe spacer features 514. The formation of the spacer features 514 shownin FIG. 5E, may occur during operation 308, when a second protectorlayer disposed over the hard mask layer 504 is patterned. The spacerfeatures 514 may be an embodiment of the second protector layer ofmethod 300.

Referring now to FIG. 5F, shown therein is the wafer 501 after the firstprotector layer 506 is removed, leaving spacer features 514A, 514B,514C, and 514D disposed above the hard mask layer 504. A portion of thesubstrate 500 may be exposed through an exposed portion of the opening512 and other comparable openings previously formed in the hard masklayer 504. As shown in FIG. 5G, a second patterning layer 516 is formedover the wafer 501 such that it covers the hard mask layer 504 as wellas the spacer features 514. During operation 310 of method 300, aplurality of openings may be formed in the second patterning layer 516.As illustrated in FIG. 5G, elongate openings 518A, 518B, 518C, and 518Dmay be formed into the patterning layer 516 by a photolithographicprocess. Each of the openings 518 may expose at least a portion of thehard mask layer 504 and a portion of one of the spacer features 514. Theoverlapping geometries of the opening 518A formed in the secondpatterning layer 516 and the spacer features 514 forms a plurality ofopenings, including an opening 520 and an opening 522. The openings 520and 522 may be aligned along a common axis 523. The opening 522 may bean assist feature defined by the geometries of the opening 518A and thespacer features 514A and 514B. The dimensions of the assist featureopening 522 may be such that the opening 522 is not intended to bepatterned into the hard mask layer 504. In other embodiments, theopening 522 may be patterned into the hard mask layer 504 duringsubsequent processing.

At operation 312, the pattern formed by the openings 518 and the spacerfeatures 514 may be etched into the hard mask layer 504 when the wafer501 is exposed to a second selective etch process that etches theexposed portions of the hard mask layer 504 at a significantly fasterrate than the exposed portions of the spacer features 514. After theselective etch process is performed and the second patterning layer 516and the spacer features 514 are removed, the wafer 501 may appear asillustrated in FIG. 5H. FIG. 5H shows intact portions of the hard masklayer 504 and exposed portions of the underlying substrate 500 and thedevice layer 502. The exposed portions may be defined by the openings512, 520, and 522 along the other openings depicted in FIG. 5H. Atoperation 314, and etch process may be performed to remove exposedportions of the device layer 502. In the depicted embodiment, theopening 522 does not expose the device layer 502 and so does not causethe device layer 502 to be etched. In such an embodiment, the opening522 may be an assist feature included to increase the fidelity ofpattern transfer. A result of the patterning process of the method 300may be seen in FIG. 5 by which depicts the substrate 500 and a pluralityof cut features, such as transistor gates, formed in the device layer502.

Referring now to FIG. 6, shown therein is a flowchart of a method 600,according to some aspects of the present disclosure. Like the methods100 and 300 of FIGS. 1 and 6, respectively, the method 600 isillustrated as a plurality of steps or operations. Embodiments of themethod 600 may include additional or alternative operations before,after, in between, or as part of the enumerated operations. Someembodiments of the methods described herein may omit one or more of theenumerated operations.

Accordingly, an embodiment of the method 600 may begin at operation 602when a first protector layer disposed over a hard mask layer ispatterned. In some embodiments, a second protector layer may be formedafter the patterning of the first protector layer and before anyadditional patterning layers are disposed over the first protectorlayer. At operation 604, a first opening in a first patterning layer maybe formed to expose a first portion of a first protector layer and afirst portion of a second protector layer. Method 600 may continue whenthe first portion of the first protector layer and the first portion ofthe second protector layer are exposed to a first selective etch to forma first protector layer opening in the first protector layer, atoperation 606. In some embodiments, an additional etch process isperformed to etch the portion of the hard mask layer exposed by thefirst protector layer opening.

At operation 608, a second opening in a second patterning layer may beformed over the wafer to expose a second portion of the first protectorlayer and a second portion of the second protector layer. The secondportion of the second protector layer and the second portion of thefirst protector layer to may be subjected to a second selective etch toform a second protector layer opening in the second protector layer, atoperation 610. The second protector layer opening may expose a portionof the device layer. And at operation 612, the exposed portions of thehard mask layer may be etched to form a first hard mask layer openingand a second hard mask layer opening. Another etch process may beperformed to remove exposed portions of the device layer through thefirst and second hard mask layer openings.

To more clearly describe the method 600, reference will now be made toFIGS. 7A-G, which depict a series of top view illustrations of a wafer701 during a fabrication process such as an embodiment of the method600. As shown in FIG. 7A, the wafer 701 may include a first protectorlayer 710 (including protector layer features 710A, 710B, and 710C. Asecond protector layer 712 is formed on the wafer 701, and may includemultiple exposed portions including protector layer portions 712A and712B. As is shown in subsequent figures, beneath the protector layers710 and 712, the wafer 701 may include a substrate 700 and a devicelayer 702. The substrate 700 may have one or more material layersdisposed thereon that are interposed between the top surface of thesubstrate 700 and a bottom surface of the device layer 702. The devicelayer 702 may be patterned into a plurality of lines similar to thedevice layer 202 shown in FIG. 2B.

As shown in FIG. 7B, a first patterning layer 714 may be formed over thewafer 701, such that the patterning layer 714 at least partially coversthe protector layers 710 and 712. The patterning layer 714 may be aphotoreactive material layer. Openings may be formed in the firstpatterning layer 714, including elongate openings 716A, 716B, and 716C,by a photolithographic process including operations of exposure anddevelopment, which may be part of operation 604. The opening 716A, 716B,and 716C, collectively referred to as openings 716, may be elongateopenings as depicted, while having other shapes in other embodiments.The openings 716 may be substantially identical to each other or includea plurality of different shapes. As illustrated in FIG. 7B, the opening716A exposes multiple portions of the underlying protector layers 712and 710. The overlapping geometries of the opening 716A and theprotector layer features 710A, 712A, and 710B forms an area 718. Whenthe wafer 701 is exposed to a selective etch that selectively etches thematerial of protector layer 712, at operation 606, the area 718 may beetched to produce a window or opening 720 formed in the protector layer712 such that a portion of the hard mask layer 704 is exposed, as shownin FIG. 7C. As shown in FIG. 7C, a plurality of openings like theopening 720 may be formed in the protector layer 712 to expose theunderlying hard mask layer 704. In some embodiments of the method 600,and etch process may be performed to remove the exposed portions of thehard mask layer 704, before additional processing is performed, such asthe formation and patterning of a second patterning layer over theprotector layers 710 and 712, at operation 608. In the depictedembodiment, the pattern defined by the opening 720 (and the otherillustrated openings of FIG. 7C) is not etched into the hard mask layer704 at this time in the method 600.

Referring now to FIG. 7D, a second patterning layer 722 may be formedover the wafer 701 such that it covers the protector layers 710 and 712and the openings formed in the protector layer 712. At operation 608,openings 724A, 724B, 724C, and 724D may be formed in the patterninglayer 722. The patterning layer 722 may be a photoresist layer or otherphotoreactive layer. The openings 724 may expose portions of theprotector layers 710 and 712. As illustrated in FIG. 7, the openings 724expose portions of the protector layer features 710A, 710B, and 710C aswell as protector layer features 712A and 712B.

As shown in FIG. 7D, the opening 724 and the protector feature 712Adefine an area 726 and a plurality of similar areas. By using aselective etch process at operation 610, the exposed portions of theprotector layer 710 may be etched without significantly etching theexposed portions of the protector layer 712. The selective etch processmay form openings in the protector layer 710 like the exemplary opening728, as shown in FIG. 7E, which further illustrates a plurality of suchopenings formed in the protector layer 710 in addition to openingsformed in the protector layer 712, like the opening 720. FIG. 7Eillustrates the wafer 701 after the selective etching to remove exposedportions of the protector layer 710 and after removal of the secondpatterning layer 722. As shown in FIG. 7E, the wafer 701 includes aplurality of openings like the opening 720 and 728 and other openings inthe protector layers 710 and 712 that expose portions of the hard masklayer 704.

As shown in FIG. 7F, the wafer 701 is exposed to an etch process thatremoves these exposed portions of the hard mask layer 704, therebyexposing the underlying substrate 700 and the plurality of parallelfeatures of the device layer 702. The etch process may be a selectiveetch process that etches the hard mask layer 704 at a significantlyfaster rate than the etch process etches either the protector layer 710or the protector layer 712. In some embodiments, rather than etch theportions of the hard mask layer 704 exposed by openings in the protectorlayer 710 at the same time as the portions of the hard mask layer 704exposed by openings in the protector layer 712, separate etch steps maybe performed for each. For example, after the opening 720 is formed inthe protector layer 712A is shown in FIG. 7C, an etch process may beused to transfer the geometry of the opening 720 into the hard masklayer 704, thereby exposing the underlying substrate 700 and the devicelayer 702. In such an embodiment, when the second patterning layer 722is removed, portions of the device layer 702 may already be exposedthrough the protector layer 712.

Referring now to FIG. 7G, prior to etching the exposed portions of thedevice layer 702, the remaining portions of the protector layers 710 and712 may be removed in some embodiments, such that the hard mask layer704 functions as an etch mask rather than the remaining portions of theprotector layer 710 and 712. After the exposed portions of the parallellines of the device layer 702 are removed, the remaining hard mask 704may be removed as shown in FIG. 7H. The etched portions of the devicelayer 702 may cut or separate lengths of the parallel lines. While theopenings 720 and 728, and the other similar openings formed in theprotector layers 710 and 712, are depicted as spanning two parallellines of the device layer 702, other embodiments may span more or fewerparallel lines or other features.

Another embodiment of the method 600 is described herein with respect toFIGS. 8A-G. Shown therein is a wafer 801 having protector layers 810 and812 formed thereon. As illustrated in FIG. 5A, the protector layer 810is patterned into protector layer features 810A, 810B, and 810C. Theprotector layer 812 is patterned into protector layer features 812A and812B. The protector layers 812 and 810 may be non-overlapping materiallayers that form a continuous surface over the wafer 801. The depictedsurface of the protector layers 810 and 812 may be a continuous planarsurface. One or more of the protector layers 810 and 812 may be formedof operation 602 of the method 600.

Referring now to FIG. 8B, shown therein a first patterning layer 814 maybe formed over the wafer 801, such that the patterning layer 814 atleast partially covers the protector layers 810 and 812. The patterninglayer 814 may be a photoreactive material layer. Openings may be formedin the first patterning layer 814, including elongate openings 816A,816B, and 816C, by a photolithographic process including operations ofexposure and development, which may be part of operation 604. Theopenings 816A, 816B, and 816C, collectively referred to as openings 816,may be elongate openings as depicted, while having other shapes in otherembodiments. The openings 816 may be substantially identical to eachother or may include a plurality of different shapes. As illustrated inFIG. 8B, the opening 816A exposes multiple portions of the underlyingprotector layers 812 and 810. The overlapping geometries of the opening816A and the protector layer feature 812A form and define an area 818.

When the wafer 801 is exposed to a selective etch that selectivelyetches the material of protector layer 810, at operation 606, the area818 may be etched to produce a window or opening 820 formed in theprotector layer 810 such that a portion of the hard mask layer 804 isexposed, as shown in FIG. 8C. As shown in FIG. 8C, a plurality ofopenings like the opening 820 may be formed in the protector layer 810to expose the underlying hard mask layer 804, as defined by thegeometries of the openings 8126 in the first patterning layer 814 andthe individual features of protector layer 812. In some embodiments ofthe method 600, an etch process may be performed to remove the exposedportions of the hard mask layer 804 before additional processing isperformed, such as the formation and patterning of a second patterninglayer over the protector layers 810 and 812, at operation 608. In thedepicted embodiment, the pattern defined by the opening 820 (and theother illustrated openings of FIG. 8C) is not etched into the hard masklayer 804 at this time in the method 600. FIG. 8D shows the result afterremoval of the first patterning layer 814 from the wafer 801.

Referring now to FIG. 8E, a second patterning layer 822 may be formedover the wafer 801 such that it covers the protector layers 810 and 812and the openings formed in the protector layer 810. At operation 608,openings 824A and 824B may be formed in the patterning layer 822. Thepatterning layer 822 may be a photoresist layer or other photoreactivelayer, patterned by photolithography. The openings 824 may exposeportions of the protector layers 810 and 812. As illustrated in FIG. 8E,the openings 824 overlap with the opening 820 and other similar openingspreviously formed in the protector layer 810, which exposes portions ofthe hard mask layer 804. The overlapping geometries of the opening 824Aand the exposed portions of the hard mask layer 804 and protectorpattern features 810A and 810B define an area 826 and three similarareas in the portion of the wafer 801 shown in FIG. 8E.

As shown in FIG. 8F, the selective etch process at operation 610 mayremove exposed portions of the protector layer features 812A and 812Bfrom the area 826 to produce an opening 828 that exposes the hard masklayer 804 underneath. The exposed portions of the protector layer 812may be etched without significantly attaching the exposed portions ofthe protector layer 810 or the hard mask layer 404. The material layersthat provide the protector layer 810, the protector layer 812, and thehard mask layer 404 may each be made of a different material havingdifferent selectivities to the etchant used in operation 610. Forexample, the protector layer 810 may be formed from silicon oxide, whilethe protector layer 812 is formed from silicon nitride and the hard masklayer 404 is formed from titanium nitride. Other combinations ofmaterials may be used in other embodiments. The selective etch processmay form openings in the protector layer 812 like the exemplary opening828, as shown in FIG. 8F, which further illustrates a plurality of suchopenings formed in the protector layer 812 in addition to openingsformed in the protector layer 810, like the opening 820, as thepatterning layer 822 is removed from the wafer 801. Thus, FIG. 8Fillustrates the wafer 801 after the selective etching to remove exposedportions of the protector layer 812 and after removal of the secondpatterning layer 822. As shown in FIG. 8F, the wafer 801 includes aplurality of openings like the opening 820 and 828 and other openings inthe protector layers 810 and 812.

As shown in FIG. 8G, the protector layers 810 and 812 may be removedfrom off the hard mask layer 804. FIG. 8G shows a combined opening 830resulting from the merging of the openings 820 and 828 as shown in FIG.8F when the hard mask layer is exposed to an etch process. Additionally,isolated openings like the opening 832 may also be present as a resultof the etching process to which the hard mask layer 804 is subjected,during operation 610 of the method 600. The wafer 801 is exposed to anetch process that removes the exposed portions of the hard mask layer804, thereby exposing the underlying substrate 800 and the plurality ofparallel features of the device layer 802. The etch process may be aselective etch process that etches the hard mask layer 804 at asignificantly faster rate than the etch process etches either theprotector layer 810 or the protector layer 812. The openings 830, 832,and other illustrated openings expose portions of the substrate 800 andthe device layer 802. In the depicted embodiment, the device layer 802is a patterned layer that includes a plurality of parallel linefeatures.

Referring now to FIG. 8H, the exposed portions of the parallel lines ofthe device layer 802 may be removed by an etch process according tooperation 612 of the method 600. The etch process may remove portions ofthe device layer 802 so as to cut the parallel lines of the device layer802. The cut to the parallel lines of the device layer 802 may be lessthan 16 nm in some embodiments. Embodiments of the method 600, andembodiments of the other methods described herein, may be used togenerate separations between the parallel lines or other features of thedevice layer 802 that could not be realized or would be difficult torealize by direct patterning of the device layer 802, such as that usedto create the parallel lines shown in FIG. 8H Removed, the remaininghard mask 804 may be removed as shown in FIG. 8H. The etched portions ofthe device layer 802 may cut lengths of the parallel lines. While theopenings 830 and 832, and the other similar openings formed in the hardmask 804, are depicted as spanning two parallel lines of the devicelayer 802, other embodiments may span more or fewer parallel lines.

The patterns formed by the openings 820 and 828, as shown in FIG. 8F,may result in the twist patterns 834A and 834B and the tight cut-to-cutpattern 836. The twist patterns 834A and 834B produce a staggeredpattern in which the location of a cut can vary from parallel line toparallel line of the device layer 802. Other patterns may be producedusing the methods described herein.

In some embodiments, the device layer 802 (and other device layersdescribed herein) may serve as etch masks for subsequent processingperformed to the substrate 800 or to one or more material layersdisposed in between the device layer 802 and the substrate 800.

Although some embodiments of the present disclosure have been describedin detail, those skilled in the art should understand that they may makevarious changes, substitutions and alterations herein without departingfrom the spirit and scope of the present disclosure. Accordingly, allsuch changes, substitutions and alterations are intended to be includedwithin the scope of the present disclosure as defined in the followingclaims. Additionally, combinations of features from the disclosedembodiments are within the scope of the present disclosure. In theclaims, means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents, but also equivalent structures.

In one exemplary aspect, the present disclosure is directed to a methodof patterning a device layer. The method includes patterning a protectorlayer disposed over a hard mask layer and forming a first opening in afirst patterning layer to expose a first portion of the protector layerand a first portion of the hard mask layer. The first portion of theprotector layer and the first portion of the hard mask layer are exposedto a first selective etch to form a first hard mask layer opening in thefirst portion of the hard mask layer. The method further includesforming a second opening in a second patterning layer to expose a secondportion of the protector layer and a second portion of the hard masklayer, exposing the second portion of the protector layer and the secondportion of the hard mask layer to a second selective etch to form asecond hard mask layer opening in the second portion of the hard masklayer, and etching exposed portions of the device layer through thefirst hard mask layer opening and the second hard mask layer opening.

In another exemplary aspect, the present disclosure is directed toanother method of patterning a device layer. The method includespatterning a first protector layer disposed over a hard mask layer andforming a first opening in a first patterning layer to expose a portionof the first protector layer and a first portion of the hard mask layer.The portion of the first protector layer and the first portion of thehard mask layer are exposed to a first selective etch to form a firsthard mask layer opening in the hard mask layer. A second protector layerdisposed over the hard mask layer is patterned. The method furtherincludes forming a second opening in a second patterning layer to exposea portion of the second protector layer and a second portion of the hardmask layer and exposing the portion of the second protector layer andthe second portion of the hard mask layer to a second selective etch toform a second hard mask layer opening in the hard mask layer. Exposedportions of the device layer are exposed through the first hard masklayer opening and the second hard mask layer opening.

In another exemplary aspect, the present disclosure is directed toanother method of patterning a device layer. The method includes forminga first opening in a first patterning layer to expose a first portion ofa first protector layer and a first portion of a second protector layerand exposing the first portion of the first protector layer and thefirst portion of the second protector layer to a first selective etch toform a first protector layer opening in the first protector layer. Asecond opening in a second patterning layer is formed to expose a secondportion of the first protector layer and the second portion of thesecond protector layer. The method further includes exposing the secondportion of the second protector layer and the second portion of thefirst protector layer to a second selective etch to form a secondprotector layer opening in the second protector layer and etchingexposed portions of the device layer through a first hard mask layeropening and a second hard mask layer opening.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand the aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of theembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure.

What is claimed is:
 1. A method comprising: forming a device layer overa substrate; forming a hard mask layer over the device layer, whereinforming the hard mask layer over the device layer includes forming thehard mask layer directly on the device layer; forming a patternedprotector layer over the hard mask layer, wherein forming the patternedprotector layer over the hard mask layer includes forming the patternedprotector layer directly on the hard mask layer; forming a firstpatterned material layer over the patterned protector layer, the firstpatterned material layer defining a first opening exposing a firstportion of the hard mask layer; removing the first portion of the hardmask layer to expose a first portion of the device layer; removing thefirst patterned material layer; forming a second patterned materiallayer over the patterned protector layer, the second patterned materiallayer defining a second opening exposing a second portion of the hardmask layer; removing the second portion of the hard mask layer to exposea second portion of the device layer; removing the second patternedmaterial layer; and removing the first portion and the second portion ofthe device layer.
 2. The method of claim 1, wherein the first portion ofthe hard mask layer is exposed after the forming of the patternedprotector layer over the hard mask layer.
 3. The method of claim 1,wherein the first portion of the device layer is covered by the secondpatterned material layer after the forming of the second patternedmaterial layer over the patterned protector layer.
 4. The method ofclaim 1, wherein the second portion of the hard mask layer is covered bythe first patterned material layer after the forming of the firstpatterned material layer over the patterned protector layer.
 5. Themethod of claim 1, wherein the removing of the first patterned materiallayer occurs prior to the forming of the second patterned material layerover the patterned protector layer.
 6. The method of claim 1, wherein afirst portion of the substrate is exposed after the removing of thefirst portion of the device layer.
 7. The method of claim 1, furthercomprising removing the patterned protector layer after the removing ofthe second portion of the hard mask layer to expose second portion ofthe device layer.
 8. A method comprising: forming a device layer over asubstrate; forming a hard mask layer over the device layer; forming apatterned protector layer over the hard mask layer; removing a firstportion of the hard mask layer to expose a first portion of the devicelayer; forming a spacer layer on the exposed first portion of the devicelayer; forming a first patterning layer over the spacer layer, the firstpatterning layer defining an opening that exposes a first portion of thespacer layer and a second portion of the hard mask layer; and removingthe second portion of hard mask layer to expose a second portion of thedevice layer while using the first portion of the spacer layer as amask.
 9. The method of claim 8, further comprising removing the secondportion of the device layer to expose a portion of the substrate. 10.The method of claim 9, further comprising removing the first portion ofthe spacer layer prior to the removing of the second portion of thedevice layer to expose a portion of the substrate.
 11. The method ofclaim 8, wherein the forming of the first patterning layer over thespacer layer includes forming the first patterning layer directly on thespacer layer.
 12. The method of claim 8, further comprising removing thehard mask layer after the removing of the second portion of hard masklayer to expose the second portion of the device layer while using thefirst portion of the spacer layer as the mask.
 13. The method of claim8, wherein the portion of the hard mask layer is exposed after theforming of the patterned protector layer over the hard mask layer. 14.The method of claim 8, wherein the forming of the spacer layer on theexposed first portion of the device layer includes forming the spacerlayer directly on the patterned protector layer.
 15. The method of claim8, further comprising removing the patterned protector layer after theforming of the spacer layer on the exposed first portion of the devicelayer.
 16. A method comprising: forming a device layer on a substrate;forming a hard mask layer over the device layer; forming a protectorlayer over the hard mask layer; forming a first patterning layer overthe protector layer; removing a first portion of the first patterninglayer to expose a first portion of the protector layer; removing thefirst portion of the protector layer to expose a first portion of thehard mask layer; forming a second patterning layer over the protectorlayer; removing a first portion of the second patterning layer to exposea second portion of the protector layer; removing the second portion ofthe protector layer to expose a second portion of the hard mask layer;and removing the first portion of the hard mask layer and the secondportion of the hard mask layer, wherein the removing of the firstportion of the hard mask layer and the second portion of the hard masklayer exposes a portion of the substrate and a portion of the devicelayer.
 17. The method of claim 16, further comprising removing a secondportion of the first patterning layer after the removing of the firstportion of the protector layer to expose the first portion of the hardmask layer.
 18. The method of claim 16, further comprising removing asecond portion of the second patterning layer after the removing of thesecond portion of the protector layer to expose the second portion ofthe hard mask layer.
 19. The method of claim 16, wherein the removing ofthe first portion of the hard mask layer and the second portion of thehard mask layer includes using the a third portion of the protectorlayer as a mask.
 20. The method of claim 19, further comprising removingthe third portion of the protector layer after the removing of the firstportion of the hard mask layer and the second portion of the hard masklayer.